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Capacity, the Key to Battery Runtime

A look at emerging rapid-test technologies for deep-cycle lead-acid batteries
By Isidor Buchmann, Cadex Electronics Inc.

The secret of battery runtime lies in the capacity. Capacity defines the energy a battery can hold. The definition for capacity is usually given in ampere-hours (Ah); it specifies the elapsed time when discharging a battery at a calibrated current to the end-of-discharge voltage. Portable batteries commonly use a one-hour discharge; larger batteries are rated at either a 5 or 20-hour discharge.

Lead acid batteries come in two basic architectures: deep cycle and starter types. The deep cycle battery is designed for maximum capacity and high cycle count. This is achieved by installing thick lead plates. Typical applications are golf carts, wheelchairs, people movers, scissor lifts and RVs. Starter batteries, in comparison, are made for maximum CCA (cold cranking amp). The battery maker obtains this by adding extra plates to get a large surface area for maximum conductivity. Capacity and deep cycling are less important for automotive because the battery is being recharged while driving. If continuously cycled, the thin lead plates of the starter battery would wear-down rather quickly. As a rule of thumb, the heavier the battery, the more lead it contains and the longer it will last.

What is the difference between Capacity and CCA?
The characteristics of the lead acid battery can best be explained by making capacity responsible for energy and CCA for delivery. Capacity and CCA do not age at the same pace. The CCA tends to stay high through most of the battery’s life, and then drops quickly towards the end. This often leaves us stranded when all of a sudden the car won’t start in the morning. In comparison, capacity decreases gradually. A new battery is designed to deliver 100% of its rated capacity. As the battery ages, the capacity steadily drops and it should be replaced when the reading falls below 70%. The reader will soon realize that capacity measurement is a more reliable state-of-health indicator than CCA.

Let’s look at the aging mechanism of capacity and CCA with graphic illustrations. Figure 1 shows two lead acid batteries, one with high capacity and one that has aged. The build-up of so-called “rock content” as part of aging robs the battery of usable energy although it may still provide good cranking power. Figure 2 illustrates a battery with high and low CCA by simulating free-flowing and restricted taps.

The third criterion of battery runtime is state-of-charge (SoC). The battery capacity is always measured on a fully charged battery and the most simplistic method of estimating SoC is reading the open terminal voltage (OTV). This approach is accurate if the battery has rested for at least four hours after charge or after applying a load. The rather long rest period is the required recovery time to pacify a battery when disturbed. The reader should also be aware that different plates composition alter the OTV reading. Calcium raises the voltage by 5-8%, affecting SoC estimation. Calcium is an additive that helps in making the battery maintenance-free.

Battery rapid-test methods
Battery capacity is commonly measured by applying a full discharge. While this method provides accurate readings, it is cumbersome, time consuming and wears the battery down unnecessarily. During the last 15 years, several rapid-test methods have emerged that eliminate the need for discharge, so the manufacturers claim. Introduced in 1992, AC conductance became popular in measuring conductance, from which CCA is estimated. This non-invasive method was hailed as a major breakthrough because the test only takes a few seconds and the instrument stays cool. Unfortunately, AC conductance is unable to read capacity and is of limited use for deep cycle batteries.

During the last five years, critical progress has been made towards capacity estimations. Cadex has developed a battery rapid-tester based on multi-model electrochemical impedance spectroscopy (Spectro™). The Spectro CA-12 injects 24 frequencies ranging from 20-2,000 Hertz. The signals are regulated at 10mV to stay within the thermal battery voltage of lead acid. The 24 slices from the frequency excitations are compared and the minute nuances analyzed. The instrument completes 40 million transactions during the short 15-second test.

Electrochemical impedance spectroscopy (EIS) is not new. Equipment using this technology has been in use for decades. A full-fledged EIS requires dedicated instruments and a computer to analyze the data. The set-up is expensive, requires trained staff for analysis and is so large that the machinery is moved on wheels. Furthermore, long calculation times make the system unsuitable for commercial use. The Spectro CA-12 has solved these problems by using powerful digital signal processors, but the heart of the engine lies in the patented algorithm.

What are typical battery problems?
Let’s look at the most common battery problems and evaluate how modern battery rapid-testers can detect these deficiencies. One can immediately see the benefit of knowing the capacity.

Low charge. A low charge reduces the drive power and the battery appears weak. Checking a low-charge battery with a discharge unit will show low capacity. Rapid testers such as the Spectro CA-12 are able to measure the capacity with a SoC as low as 40%. If lower, the instrument will prompt to charge and retest.

Low capacity. This low capacity battery will likely have good conductivity and strong torque. The voltage checks out fine and everything appears normal except the short runtime. Knowing the capacity on an aging deep cycle battery is very important because it’s the best indication when a battery should be replaced.

Mismatched set. Batteries do not age at an equal pace. Like the links of a chain, the battery with the lowest capacity will govern the runtime. Battery testers reading capacity can identify low performers and allow a timely replacement. The high performers can be regrouped for continued service.

As encouraging as battery rapid testing may be, the reader needs to be reminded that rapid-testers, such as the Spectro CA-12, are not universal instruments capable of measuring the capacity of any battery that will come along; they need a battery-specific matrix as a reference. On purchase of such a unit, the instrument includes one or several matrices that are automatically matched with the selected battery. Cadex is in the process of expanding the matrix library to eventually include all major battery types.

In time, measuring battery performance through non-invasive means will become the acceptable standard, making discharge methods redundant. Typical applications are: checking batteries to reduce false warranty returns, preventing unexpected downtime by assessing battery state-of-health before a breakdown occurs, and improving the reliability of battery operated rental equipment.

Designers of battery rapid-test methods tend to be overly optimists and create targets that may not be achievable outside the laboratory. However, multi-model electrochemical impedance spectroscopy represents a great leap forward and opens the door to an entirely new way of battery testing.

About the Author

Isidor Buchmann, founder and CEO of Cadex Electronics Inc., has studied the behavior of rechargeable batteries in practical, everyday applications for two decades. As an award-winning author of many articles and books on the subject, Mr. Buchmann has delivered battery-related technical papers around the world.

Cadex Electronics Inc. is a Canadian company specializing in the design and manufacturing of advanced battery testing instruments. For product information please visit



Santa Fe Springs, Calif., April 11, 2012 – Trojan Battery Company, the world’s leading manufacturer of deep-cycle batteries, today launched “Trojan Tips,” its video tutorial series created to provide in-depth information focusing on a variety of battery topics such as deep-cycle battery technologies, maintenance practices, charging procedures and safety when handling batteries. “Trojan Tips” is designed to expand awareness of deep-cycle battery technology.

The first “Trojan Tips” video tutorial can be viewed at

A new “Trojan Tips” video tutorial will premiere each month throughout 2012 on the Trojan Battery corporate Web site. The first “Trojan Tips” video, which debuts today, reviews the various battery technologies available on the market today, and what to consider when selecting a battery for a particular application. The public, as well as Trojan distributors, dealers and customers can log onto the Trojan Web site to view the video tutorials and learn more about a variety of deep-cycle battery topics.

“One of the most important features of electrically powered equipment, and probably one of the most ignored, is the battery,” said Vicki Hall, Trojan’s director of quality and technical services, and host of the “Trojan Tips” educational series. “The battery is the heart of any piece of electric equipment that relies on batteries for power. When a battery fails in a golf car, scissor lift or floor cleaning machine for example, it can make or break a day on the course or impact profitability on the job site. Proper understanding of this technology and maintenance practices are key to getting the most out of a battery investment.”

Trojan developed the “Trojan Tips” series to educate the public on a variety of important battery-related subjects that can positively impact the performance and longevity of deep-cycle batteries used to power electrical equipment. Topics such as selecting the right battery, maintenance techniques and appropriate charging and equalization guidelines are just a few of the issues that will be addressed during the video tutorial series.

About Trojan Battery Company
Trojan Battery Company is the world’s leading manufacturer of deep-cycle batteries and a battery technology pioneer, having built the first golf car battery in 1952. Trojan batteries provide power for a wide variety of golf, industrial, renewable energy, recreational and auxiliary power applications. Founded in 1925, the company is ISO 9001:2008 certified with operations in California and Georgia, and maintains two of the largest and most extensive research and development centers in North America dedicated to engineering new and advanced battery technology. For more information on Trojan Battery Company, visit


Focus on Battery Health

By Mick Abraham

Solar power has been romanticized as a “green technology”, but truly in-dependent power also includes lots of “black technology”. An off-grid energy system may have clean non-polluting solar modules smiling at the sun, but it also includes heavy chemical batteries containing toxic substances like lead and sulfuric acid. Batteries are the dark industrial underbelly of off-grid renewable energy systems.

I’ve had a love/hate relationship with deep cycle batteries ever since buying my first one in 1984. Chemical batteries will remain essential to in-dependent energy for many years to come, but they also represent the number one problem area. Performance gradually degrades in ways that are barely noticeable at first, but the pack eventually reaches an “avalanche point” where the battery capacity falls off a cliff. This causes a crisis for the system owner which requires emergency money transfusions to their battery vendor.

Batteries are so problematic that those who rely on them can get discouraged. I’ve become acquainted with many “off gridders” as customers who later developed into friends, so I know a bit about their frustrations. Many have reached the point of selling their homes, bringing in costly line extensions from the grid, and taking other drastic measures. To me, each of these events represented a failure for myself, for the off-grid energy industry, and for its technology. Watching my friends and customers endure their battery disappointments, I gradually developed a personal quest to learn more about batteries and to look for ways to reduce these problems. My quest has now been under way for more than ten years, and it has changed my alternate energy business more than once.

In 1997 I introduced the PowerPulse® electronic sulfation dissolver to the alternate energy world, and I’ve shipped over 7,000 of those units since that time. Since independent power systems sometimes can’t recharge their batteries promptly, lead sulfate compounds can develop a covalent bond to the battery plates which cannot be reversed with normal recharge methods. The sulfate busters use a well understood means to resonate and dissolve the crystal form of lead sulfate.

PowerPulse (and the competing clones which soon followed) is now a common battery enhancement, but battery longevity has continued to disappoint. Even my PowerPulse customers still come up against battery surprises. It’s also not easy to confirm what the pulse device is doing or if it’s still working. I’m a believer but others have attacked this product category as “snake oil”.

In 2005, I began testing a new battery enhancement device which may prove more significant than the sulfate dissolver. This is an automatic battery balancer called BattEQ™. The product is based on research work at the University of Illinois. SmartSpark® Energy Systems, Inc. has licensed this and other patents, and serves as a distributor & factory rep for Smart Spark.

SSES builds several different versions of their equalizer. The first one that I rolled out is optimized for 6-volt batteries, such as the popular “L-16 floor scrubber” or “T-105 golf cart” batteries. Other equalizers balance to the 12 volt increment for different type battery banks.

BattEQ rapidly switches a bank of energy storing capacitors from one increment of the battery string to the next. When the capacitors encounter a segment which exhibits voltage above the average, a bit of energy is absorbed. When the caps encounter a segment which is below the average voltage, they dump their stored energy. The result is a “flywheel effect”; each segment tracks the others with nearly identical voltage—with important effects on battery health and performance.

Alpha Telecomm has also licensed the same “flying capacitor” technology from the university; search for the AlphaGuard™. In some ways, AlphaGuard is more “civilized” than BattEQ, but the balancer bandwidth with AlphaGuard is too low for house sized battery banks. BattEQ pumps more energy per dollar than any other balancer that I’ve seen.

Voltmeter tests are an easy way to confirm equalizer function; if a clamp style DC ammeter is available, one can clip around each balancer lead to read the energy throughput. The amperage readings are typically highest when the balancer is first installed; even on brand new batteries off the same shipping pallet, I never fail to observe a few amps of energy transfer.

Combining all my various prior efforts, my gleam in the eye is pack level sulfate dissolving (easy & relatively cheap), combined with balance at the level of individual two volt cells. The last part of this is much more of a challenge, so my next step is to just try for cell level information.

I’ve now got the ball rolling on a special version of the PakTrakr, to capture the voltage of each individual cell in a battery string (this assumes that one has access to the individual cell terminals, of course). shows their standard offering (which I can also supply for battery users who have 6 volt or 12 volt monoblocs). I plan to post a flyer on the two volt version on my Top Floor before long. The Paktrakr products should particularly appeal to battery professionals who want a simple way to highlight battery balance issues for their customers.

The elephant in the room is this: since there is no BattEQ for individual two volt cells, what actions can we take if PakTrakr points up a single weak cell? I’ve got varying ideas in mind…of varying quality. As mentioned above, this won’t be easy but I do think it is worth working on and the next thing to do is get cell level data.

I extend my thanks to for publishing this article, and I hope to see fewer battery problems down the road. Charge!

Contact Information:

Mick Abraham, Proprietor

Voice: 800-222-7242 or 970-731-4675

Fax: 970-731-3292
Skype username: abrahamsolar
Abraham Solar Equipment
124 Creekside Place
Pagosa Springs, CO 81147


RENEWABLE POWER FOR AMATEUR RADIO (and other electronic devices)

RENEWABLE POWER FOR AMATEUR RADIO (and other electronic devices)
by Larry D. Barr, K5WLF

About the author: Larry D. Barr is an Amateur Extra class amateur radio operator, first licensed in 1966. He is uniquely qualified to write on this subject, having lived offgrid for 19 months with the majority of his electricity provided by a Wincharger 1222H wind generator. Larry is a journey level electrician, an alternative energy systems designer and the former editor of Energy Self Sufficiency Newsletter. His pickup mounted, solar powered ham radio installation was featured in the American Radio Relay League’s “We Do That” video series and on their website. Currently employed as the Planetarium Manager for Tarleton State University in Texas, Larry continues to be active in renewable energy and looks forward to living offgrid again in the near future.

Because of my interest and involvement in renewable energy, I’m often asked by other amateur radio (ham) operators about the best way to run their stations on renewable energy sources. Most of these queries pertain to solar, or photovoltaic (PV), sources, but we’ll also mention wind and minihydro in addition to PV in this article.

The good news is that modern, solid state ham rigs lend themselves extremely well to renewable power. They draw relatively little current at a nominal 12 VDC, and therefore require fairly modest expenditures in generating devices.

The bad news is that hams who like the old vacuum tube (hollow state) rigs will not be able to power those old “boat anchors” without a serious layout of funds for PV panels or a much larger than usual wind generator. The old rigs simply draw too much current to be practical for operation on a renewable system.

So, let’s look at the practicality of running a modern, 100 watt, solid state transceiver like my Yaesu FT897D on a PV system. It’s easy to do – and at a relatively low cost for the solar setup.

First, let’s consider the power required to operate the radio. There are two distinctly different current requirements for the unit. One is the power required for the radio to receive incoming signals. That’s about one ampere (1A) at a nominal 12 volts direct current (12 VDC). Nominal 12VDC turns out to be somewhere in the vicinity of 12.6 VDC, for a fully charged 12 volt battery, to around 13.8 VDC which is the output of an average vehicle alternator. We’ll mostly stick with 12 VDC for this article just to make the calculations easy.

The other requirement is 22A while transmitting at the full 100 watt output level. Well, you’d think that wouldn’t take long to run down a battery, and you’d be right. But think a minute. We don’t transmit all the time. Actually, the ratio of transmit to receive in normal ham operation is right at 1:9. 10% transmit and 90% receive.

Now, we need to figure out how many Amphours (Ah) we’ll use per clock hour in normal operation. Amphours is the numbers of amps, the current, consumed over a period of one hour. It’s the way the battery capacity is rated. As I said earlier, normal radio operation is generally calculated at 90% receive and 10% transmit.

So, in 1 clock hour we’re consuming:
(1A X 0.9h) + (22A X 0.1h) = (0.9Ah + 2.2Ah) = 3.1 Ah

Figuring our 100Ah battery at 50Ah, because we don’t ever want to take the battery below 50% depth of discharge, we divide:
50Ah / (3.1Ah/hour) = 16.129 hours

Which is about 16 hours and 8 minutes from a fully charged battery. I run two 100 Ah sealed lead acid (SLA) batteries in my battery banks for a rated 200 Ah capacity and a ‘real world’ capacity of 100 Ah. That doubles my run time to about 32 hours and 16 minutes.

There are those who will disagree with me about my advice to never exceed 50% depth of discharge in a deep cycle battery. They are welcome to do so. And I will never loan one of those folks my batteries. Your batteries will last much longer and provide better service to the end of their life if you follow my advice. Each time a battery is drawn below 50% charge, it gives up a small part of its longevity. Personally, I can’t afford to replace batteries before the natural end of their life. So, I treat them well. My shack and pickup batteries are over six years old and still operating at peak efficiency.

I must mention here that manufacturers base the capacity ratings of their batteries on the assumption that the discharge will be made at a constant rate. That rate is assumed to be one twentieth (1/20) of the published Amperehour rating of the battery. In the case of our single 100Ah battery, the rate would be 5A. For our 200 Ah bank, it would be 10A. This relationship is called C (capacity) / 20. You’ll see it published simply as C/20 or ‘the C/20 rate’.

Any deviation from this C/20 rate, especially discharge rates which exceed it, will result in a different amount of power available from the battery. If we exceed the C/20 rate, the capacity of the battery will be less. In many cases, much less. It depends on the extent to which we exceed the C/20 rate of discharge.

In the case of our 100 Ah example, since our calculated rate of discharge was 3.1Ah/hour (or 3.1A), we were below the C/20 rate of 5A and should get at least the run time we calculated. However, if we were to exceed the C/20 rate, our run time would be less. How much less would be proportional to the amount above the C/20 rate that we imposed on the battery. If our discharge rate is below C/20, we may get a bit more. But let’s figure for worst case and not count on it. This phenomenon has been well documented by a gentleman named Peukert and his analysis of the effect is known as Peukert’s Theorem.

We should note, and must accept, that this does not indicate that the battery is faulty. It’s simply reacting in accordance with the laws of physics and chemistry that batteries operate under. To draw an analogy — if you bought a car and the manual stated that you could expect 25 MPG at 50 MPH, it would be unreasonable to expect that same mileage at 120 MPH. You’ve changed one of the variables in the equation and you can’t expect the result to be the same.

Now, let’s look at the PV panels and other gear required to support our FT897D on a solar electric diet.

My system consists of two UniSolar US64 amorphous panels rated at 64 watts each. They’re connected in parallel for a total of 128 watts. With the Xantrex C12 charge controller set at an output voltage of 14.2VDC – it seems high, but it’s right for the SLA batteries – that gives me about 9.01 amps to the batteries. Let’s just call it 9 amps. So, in one clock hour, I’ve put 9 amphours back into the batteries. That’s almost a 3:1 ratio of input to output.

Truth be told, I usually see about 7.4 amps, more or less, from the panels going into the battery bank. But that’s more than twice what I’m using and certainly explains why, on occasion, I’ve gone out on a radio mission with less than fully charged batteries, worked on the air for four hours or so and returned home with a fully charged battery bank. And all free, from Mother Nature.

My UniSolar panels aren’t available anymore. Unisolar has decided to dedicate their manufacturing capability to mainly Building Integrated PhotoVoltaic (BIPV) and has discontinued their line of discrete PV panels. We recently mounted a Kyocera 235 watt panel on our local ham club’s tower trailer, and if I were buying now that’s what I’d get for myself.

Let’s look at the total cost of a PV system to run the radios using the Kyocera panel.

The PV panel will run you about $375, the Schneider/Xantrex C35 controller with the CM digital display (recommended) is about $165, and a pair of PowerSonic 100 Ah SLA batteries will round out the system for $275 each or $550 for the pair. That’s a total of $1090 for the system. With proper care, the panel and the controller will last you for a lifetime. The life span of the batteries depends on you. I’ve been running mine for about six years now, and they’re still doing their job, and doing it well. If you abuse them, by discharging them below 50% capacity, or over or under charging them, their life span will decrease.

Now, let’s talk about wind power for a minute. If I were buying a wind generator today, I’d get an Air 30 turbine made by Southwest Windpower. It’s a 400 watt unit and has all the controller circuitry built in. At peak output, it’ll give you somewhere around 25 amps, and because of the integral controller, it interfaces seamlessly with a PV system. Cost is somewhere in the neighborhood of $600. If you live where wind is one of your most prevalent natural resources, you might get by with just the Air 30, but I really recommend a hybrid system that uses more than one source. Wind and PV is a great combination, for many times when the wind is blowing the most, the sun is obscured.

Minihydro is a wonderful power source if you have a year round watercourse on your property. If you don’t, just forget about it. My dream is to find a property with a year round stream on it, but unless I win the Lotto and maybe leave Texas (not likely), I’ll never find it. Don’t even fret over hydro unless you can provide your system with a reliable and continuous source of water. There aren’t many locations available with that resource and it’s best to not even think about it unless you already own it. If there’s a call for it, I’ll gladly write about minihydro at length in a future article.

OK. let’s summarize. I’ve explained how to calculate the draw of your radio. We’ve discussed the factors that control battery run time and battery life. We have talked about the initial cost of a PV system, and considered adding a wind turbine to the system. It’s easy to add other 12VDC devices, such as lighting or entertainment devices, to the system. Just do your calcs and ensure that you’re not drawing your battery bank below 50% capacity. Be sure to follow all appropriate wiring codes and make damn sure that your wiring is safe and overload protected. Enjoy the free energy that Mother Nature provides. ldb

Off grid info and components available at

Discuss Amateur radio and alternative energy topics at


Trojan Battery Introduces Single-Point Watering System For Its Flooded Batteries

SANTA FE SPRINGS, Calif., March 20, 2013 — Trojan Battery Co., the world’s leading manufacturer of deep-cycle batteries, has launched a single-point battery watering system for its line of flooded batteries for renewable energy and backup power applications. The new watering system makes maintenance of Trojan’s deep-cycle flooded batteries faster, easier and safer.

Trojan’s single-point watering kit is designed to take the guess work and mess out of properly watering flooded batteries. The flexible tube routing allows the watering system to work with various battery bank sizes and configurations. It also features an automatic valve shut-off to control the electrolyte level within each cell which prevents overwatering. In addition, the kit enables users to fill their deep-cycle batteries without having to remove the vent covers, an important safety feature which reduces the chance for contact with the battery’s electrolyte.

“Proper maintenance and periodic watering are important factors in maximizing the performance and life of Trojan deep-cycle, flooded batteries,” said Bryan Godber, senior vice president for renewable energy at Trojan Battery. “With Trojan’s new single-point watering kit, precise battery watering is made easy and can fill a set of batteries in 30 seconds, saving valuable time and money.”

The single-point watering kit comes in three configurations to fit 12V, 24V and 48V battery models. The kits are designed for single string installations with Trojan Premium, Industrial and Signature lines of flooded batteries. For systems with multiple strings in parallel, additional kits can be added at the required system voltage.

About Trojan Battery Company
Trojan Battery Company is the world’s leading manufacturer of deep-cycle batteries, offering a complete portfolio of technologically-advanced deep-cycle flooded, AGM and gel batteries that provide maximum long-lasting performance to meet the requirements of today’s advancing renewable energy systems. Trojan Battery Company, founded in 1925, is ISO 9001:2008 certified with U.S.-based operations in California and Georgia. For more information, visit


The 6v LED Lantern Flashlight

Again we address the LED flash-light topic, because it’s one of our favorite topics. This time we converted a Eveready(R) Utility Lantern. It comes with a pretty weak PR13 bulb, but we will fix that shortly.

Nice features of this flash-light is that it floats, has a shatter-proof lens, and comes with a 6v battery. It comes in a variety of colors, so if you mail order it, you never know what one you might get.

Ok, Why convert to LED? Well, as we have said in previous upgrades of tube type flashlights, a good LED will last pretty much forever, is shock proof, greatly increases brightness, and can extend battery life by 2x or more (unless you go extreme). Over the years you can save well more than the cost of the bulb in reduced battery costs.

Ever have a bulb get dimmer and dimmer till you can hardly see? Not so with LED’s. They stay bright, and then suddenly go out when battery voltage dips below the minimum needed to keep them lit. Ok, so maybe that’s a mixed blessing. Keep a spare battery handy.

So, here’s a couple of proven LED options.

TerraLUX TLE-1F MiniStar1 1-Watt 50 Lumen Replacement Bulb

TerraLUX TLE-6EX MiniStar5 5-Watt 140 Lumen Extreme LED Replacement Bulb

The 1-Watt LED is a nice visual upgrade for the old 2.38 Watt PR-13. It’s brighter, and whiter (a little blueish versus aging yellow on the PR-13). The 5-Watt Extreme LED will make you blind as a bat (without the cool sonar stuff).

Pulling out the old bulb isn’t very easy, so just take your time and gently rock the plastic carrier plug back and forth with firm pulling pressure.

There you have it! Have fun, and happy conversions. It’s a cool upgrade!

PS: There are not 32 AA batteries inside a 6v lantern battery, if you have seen the gag video claiming otherwise. There are four 1.5v “not quite D” (F) cells in series batteries inside.

Want a rechargeable “Lantern Battery”? shows that four “C Cells” will fit nicely inside. A 6v lantern battery is about 11 amp hours, so unless you can get creative, you will lose run time, but at least pick up recharge-ability. The 11amp hour “D” NiMH will also fit (a tiny bit larger in diameter than the “F”), and give you similar ah rating as the 6v Lantern Battery. Use the Dorcy 4D adapter for instant conversion!

Maha Powerex D cell 11,000mAh Rechargeable Batteries- 2 Pack

AA NiMH Precharged Rechargeable Batteries (8-Pack, 2000 mAh)

Remington makes a 6v agm Lantern Battery, but it requires a special charger:



See the following video for ideas.


Estimating Battery Charge Time from Solar

Jeff Crystal – Voltaic DIY Solar

You have a 2 Watt, 6 Volt panel and a 1,000 mAh, 3.7V battery, how long does it take to completely charge? The quick and very wrong answer would be to figure out the Watt hours of the battery (3.7 * 1Ah = 3.7 Watt hours) and divide. The reality is about 2.5 times longer.

There are three main reasons for the difference, even in ideal conditions. First, the Wattage rating on the panel is the open circuit Voltage multiplied by the peak current. When you connect a panel to a battery, the Voltage drops down to that of the load, in this case 3.7V. Finally, all the power that enters the battery does not get converted into storage energy. Some percentage is lost as heat as the process to convert the incoming power into stored power takes energy.

In field tests, we’re seeing that the combined loss factor is about 2.5. So Divide the Watt hours of your battery by the Wattage of your panel and multiply by 2.5. In our example above you would get 3.7 Watt hours / 2.0 Watts * 2.5 = 4.6 hours to fully charge. If you have cloudy conditions, your panel is not pointed at the sun or your panel’s Voltage is not well matched to your battery, this could increase.

With large-scale systems, maximum power point tracking is used to increase production efficiency. We haven’t seen any cost-effective examples in small-scale systems yet. If you know of any, please drop us a line.


Off Grid Solar Packages

Because of cheap, incomplete solar “packages” flooding the market by mass marketers of Chinese junk, we have been requested by our readers to provide a quality “everything in the box” kit, with detailed DIY instructions for installation and maintenance. We have provided these proven kits to the Caribbean, off grid hunting camps, and less developed countries where electricity, water, and other services are intermittent or non existent. Some of these systems run unattended for 6 or more months of the year, and have been in place for 5 or more years without disruption. All kits come with our complete electronic library of solar, wind, and rainwater harvesting ebooks.

The first step to buying a solar pv kit is to know your power consumption. For a whole house, this is on your electric bill, listed as your monthly kWh consumption. Divide by 30 to get a average daily consumption, then look at the packages below for a daily production that fits that range. For doing room at a time projects, use A Kill-A-Watt meter to determine the consumption of devices in that room, then pick the package that fits.

We list the raw wattage of the system, and the expected daily kWh production for 2 extremes, low end (NY – 2 full sun hours daily in winter) and high end of solar availability (Anguilla – 6 full sun hours daily in winter). Most folks will fall somewhere in between. You can determine your daily and monthly averages at

Kit #1 (RV optimized) (200 watt, .4 – 1.2 kWh daily)
1 200 watt panel
1 15 amp solar charge controller
2 12v AGM battery (100 ah)
1 300 watt SW inverter
1 wire, fuse, and connector kit
Trimetric Battery Monitor Kit

$2299 (S&H Not Included)

Kit #1 can at minimum (NY), power 10 of our LED lighting kits for 10 hours and our 12v cistern water pump for daily washing and cooking.

Kit #2 (400 watt, .8 – 2.4 kWh daily)
2 200 watt panels
1 30 amp solar charge controller
4 12v AGM battery (100 ah)
1 300 watt SW inverter
1 wire, fuse, and connector kit
Trimetric Battery Monitor

$3599 (S&H Not Included)

Kit #2 can at minimum (NY), power 10 of our LED lighting kits for 10 hours, our 12v cistern water pump for daily washing and cooking, and a laptop computer or small LCD TV for 4 hours or so.

Kit #3 (600 watt, 1.2 – 3.6 kWh daily)
3 200 watt panels
2 30 amp solar charge controllers
6 12v AGM battery (100 ah)
2 300 watt SW inverters
1 wire, fuse, and connector kit
Trimetric Battery Monitor

$5199 (S&H Not Included)

Kit #3 can at minimum (NY), power 10 of our LED lighting kits for 10 hours, our 12v cistern water pump for daily washing and cooking, and a laptop computer or small LCD TV for 8 hours or so.

Kit #4 (800 watt, 1.6 – 4.8 kWh daily)
4 200 watt panels
2 30 amp solar charge controllers
8 12v AGM battery (100 ah)
1 2000 watt SW inverter/charger/transfer switch (for gen kit)
1 wire, fuse, and connector kit
Trimetric Battery Monitor

$7499 (S&H Not Included)

Kit #4 can at minimum (NY), power 10 of our LED lighting kits for 10 hours, our 12v cistern water pump for daily washing and cooking, a laptop computer or small LCD TV for 6 hours or so, and 2 ceiling fans for 6 hours or efficient fridge.

Kit #5 (1000 watt, 2 – 6 kWh daily)
5 200 watt panels
3 30 amp solar charge controllers
10 12v AGM battery (100 ah)
1 2000 watt SW inverter/charger/transfer switch (for gen kit)
1 wire, fuse, and connector kit
Trimetric Battery Monitor

$8699 (S&H Not Included)

Kit #5 can at minimum (NY), power 10 of our LED lighting kits for 10 hours, our 12v cistern water pump for daily washing and cooking, and a laptop computer or small LCD TV for 6 hours or so and a efficient fridge.

Portability Kit
Electronics packaging optimized for portability, either appliance dolly or wagon mounted. Not as appropriate for kits 3-5.

$199 (S&H Not Included)

12v LED Lighting Kit (2w – 100 lumen)
Perfect for task lighting, these lights consume very little power, produce very little heat, and last almost forever in extreme conditions.

$37 (S&H Not Included)

12v Water Pump Kit (contains wire, fuse, and disconnect)
for cisterns or water barrels – $199 (S&H Not Included)
for wells up to 30′ deep – $550 (Motor & S&H Not Included)

Generator Charging Kit
Contains a Honda powered generator, wiring and a 3 stage battery charger for kits 1-3, or just the generator and wiring for kits 4 & 5.

eMail for price


Trojan Battery Configuration Calculator

TRJN_BatterySizingCalculatorSS (2)A few years ago I designed a online battery load calculator, but Trojan (one of our favorite off grid battery manufacturers) came out with a good configuration tool. This calculator is a tool to help you determine the model and quantity of Trojan batteries needed for your renewable energy or backup power system. The calculator recommends batteries based on your inputs and the results are ranked according to cycle life performance.




Check it out at


Trojan Deep Cycle Battery – Cast On Strap

Ever wonder what goes into the construction of a deep cycle battery? See how Trojan Battery assembles it’s batteries in the following video!

Continuing its effort to expand the public’s understanding of deep-cycle battery technology, Trojan Battery has produced a video demonstrating its new cast-on-strap (COS) manufacturing equipment. Because there are two key elements that distinguish Trojan batteries from the competition – the quality of the materials we use and our assembly/fabrication process – Trojan developed this video to illustrate the advanced technology used to manufacture our batteries and earn them the label “Made in the USA.” While most other battery manufacturers use COS machinery originally designed to produce automotive batteries, Trojan Battery commissioned the development of its COS equipment to specifically manufacture only deep-cycle batteries.

More Trojan video’s